[John Rogers]

When I set the tang sights and also the scopes on my black powder muzzle loader slug guns I set then so the top of the barrel is level. I use a 24 inch digital level that reads to .0001 degrees which if you think about it is way more accurate than shooting a 540 grain slug of lead needs to be. But as noted I set the level and the gun then turn the level around to see if the reading is the same. Fortunately I have no tapered barrels.

When you think of how small an eight foot pool or billiards table is compared to the circumference of the earth, being "level" is a minor relative thing ( 6.08 e-8 feet) or a small amount.